University of Calgary
Univ. Of Calgary: Punctuation Rules Periods
The informational site which includes helpful details concerning the rules, uses, and misuses of periods in the English language. Includes information about the period at the end of sentences as well as in abbreviations. Also, provides...
Other
Sandhills Community College: The Period
A good guide to understanding the several uses of the period in English punctuation. Includes information concerning periods in a sentence as well as abbreviations. Includes several examples.
University of Calgary
Univ. Of Calgary: Periods, Question Marks, Exclamations
This excellent resource provides information about rules, uses, and misuses of these three end marks (period, question mark, exclamation mark). Also, includes examples and short quizzes at the end of each section.